1. Technical Field of the Invention
The present invention relates to a switch device for rotating and stopping a window-opening/closing direct-current motor for a vehicle such as an automobile or a direct-current motor in the similar application, and more particularly to a switch device suitably applicable to a direct-current motor to operate on high power voltage (e.g. 42V-based electrical system).
2. Description of the Related Art
The 14V-based electric systems are employed on the existing automobiles. However, the 14V-based system in the recent situation cannot afford to supply consuming power because of the increasing number of mounting electronic apparatuses and devices. In an attempt to eliminate this, discussions have been continued globally in the forms of industry-university consortiums and the like. As a result, a consensus has been gained by adopting a treble high-voltage system, or xe2x80x9c42V-basedxe2x80x9d electrical system, wherein the safety to the human body is taken into account.
The electrical devices operable on 42V-based electrical system include a window operating/closing direct-current motor built within the door (so-called a power-window driving direct-current motor), for example.
FIG. 8A is a structural view of a conventional switch device for rotating (forward/reverse) and stopping a window-opening/closing direct-current motor while FIG. 8B is a circuit diagram of the same (see Non-patent Document 1, for example).
This switch device 1 is arranged on an armrest or the like provided on an interior side of the door at the vehicular front or rear seat. The switch device 1 of the figure is shown a state that the power-window driving direct-current motor (hereinafter referred to as xe2x80x9cdirect-current motor) 2 is in a standstill. Namely, shown is the state that the knob 3 is not operated by a vehicular passenger. Hereinafter, this state is referred to as a xe2x80x9cneutral statexe2x80x9d.
The knob 3 is arranged on a case 4 on the door side, for rotation by a predetermined angle in a clockwise and counter clockwise direction of the figure. When the knob 3 is moved clockwise, the window closes (hereinafter referred to as xe2x80x9cUP statexe2x80x9d). When it is moved counter clockwise, the window opens (hereinafter referred to as xe2x80x9cDOWN statexe2x80x9d). In case the operating force applied to the knob 3 is canceled (releasing the finger), it returns to the neutral state by the action of the spring 5 and plunger 6 buried within the knob 3, maintaining the neutral state from then on.
The lower projection 7 of knob 3 extending within the case 4 assumes the shown position when the knob 3 is in the neutral state. When the knob 3 is placed in the UP state, it swings leftward of the figure (see FIG. 10A). When the knob 3 is placed in the DOWN state, it swings rightward of the figure (not shown).
Within the case 4, there is provided a switch unit 9 mounted on a printed board 8. This switch unit 9 is to function as a xe2x80x9c2-circuit 2 contactxe2x80x9d switch of a momentary type, the exterior view of which is shown in FIGS. 9A to 9D. The switch 9 has two common terminals 11, 12 extended from one side surface of the housing 10, one normally-open terminal 13 extended from the other side surface of the housing 10, and two normally-close terminals 14, 15 extended from the bottom surface of the housing 10. These terminals 11-15 are soldered on a required conductor circuit formed on the printed board 8, and connected to a power line (hereinafter referred to as xe2x80x9c+B linexe2x80x9d) 17, a ground line 18 and the direct-current motor 2. Thus, the configuration of a circuit diagram of FIG. 8B is realized.
Within the switch unit 9, two circuits of switches A, B are mounted as shown in FIG. 8B. These switches A, B is exclusively switched over depending upon a slide position of the slider 28 arranged on an upper surface of the switch unit 9. Incidentally, xe2x80x9cexclusively switched overxe2x80x9d means that the NC (normally-close) contact of one of the switches A and B only is put in an open state (in other words, the NO (normally-open) contact of that switch only is put in a close state).
Specifically, when the slider 28 is in the position of the figure (in the xe2x80x9cneutral statexe2x80x9d), the switch A is in a close state at between a movable contact 19 and an NC contact 23 while the switch B is at between a movable contact 20 and an NC contact 24. In this state, the switches A, B assume states as per the names (NOxe2x86x92normally open, NCxe2x86x92normally close) at NO contacts 21, 22 and NC contacts 23, 24 in two sets. However, when the slider 28 moves in a direction of the leftward arrow L in FIG. 9A (in the xe2x80x9cUP statexe2x80x9d), the switch B is maintained in the close state at between movable contact 20 and NC contact 24. Furthermore, the switch A is canceled of the close state at NC contact 23, into newly a close state at between movable contact 19 and NO contact 21. Meanwhile, when the slider 28 moves in a direction of the rightward arrow R in FIG. 9A (in the xe2x80x9cDOWN statexe2x80x9d), the switch A is maintained in the close state at between movable contact 19 and NC contact 24. Furthermore, the switch B is canceled of the close state at NC contact 24, into newly a close state at between movable contact 20 and NO contact 22.
The switching action like this is caused by movement of the slider 28 and an underside geometry of the slider 28. FIG. 9C is an Xxe2x80x94X sectional view of the slider 28 while FIG. 9D is a Yxe2x80x94Y sectional view of the slider 28. The slider 28 in the Xxe2x80x94X section is formed thick-walled in the right half thereof while the slider 28 in the Yxe2x80x94Y section is formed thick-walled in the left half thereof. As will be apparent from the below explanation, the switches A and B are exclusively switched over depending upon a positional relationship of the thick-walled part.
Incidentally, FIG. 8A depicts only one of the common terminals 11, 12 and one of the normally-close terminals 14, 15. This is because the terminals are arranged front and rear on the figure, wherein the terminal on the rear is hidden invisible by the front terminal.
As explained before, the switch unit 9 functions as a xe2x80x9c2-circuit 2-contactxe2x80x9d switch of a momentary type. Namely, the movable contacts 19, 20, the NO contacts 21, 22 and the NC contacts 23, 24 are respectively connected to the common terminals 11, 12, the normally-open terminals 13 and the normally-close terminals 14, 15, thereby exclusively enabling contact-switching of two circuit 5 (switching between the movable contact 19, the NO contact 21 and the NC contact 23, and switching between the movable contact 20, the NO contact 22 and the NC contact 24).
The movable contact 19, 20 is attached on a tip of a metal-make spring leaf movable piece 25, 26. The metal-make spring leaf movable piece 25, 26 is made to be urged downward in the figure by a push button 27A, 27B (the push button 27A is for the switch A, the push button 27B is for the switch B). The push button 27A, 27B is in abutment against an underside of the slider 28 (see FIGS. 9A to 9D) movable laterally in the figure. As shown in FIG. 10A, as slider 28 moves left in the figure, the push button 27A only can be separately pressed down along the underside geometry (thick-walled part) of the slider 28. Meanwhile, the upper projection 29 of the slider 28 is engaged with the tip of a lower projection of the knob 3. The slider 28 follows the lower projection 7 of knob 3 swinging left and right (UP and DOWN states), to slide in the left and right direction in the figure.
Accordingly, in the switch device 1, when the knob 3 is pulled up into the UP state, the slider 28 slides leftward. The push button 27A, abutting against the thick-walled part of slider 28 with respect to its Xxe2x80x94X section, moves down. The switch A is placed into an open state at its movable contact 19 and NC contact 23, while the same switch A is placed in a close state at its movable contact 19 and NO contact 21, which operation is thus obtained. Meanwhile, when the knob 3 is released from the finger into a neutral state, the slider 28 slides rightward and returns to the former position. The push button 27A moves up to place the switch A into a close state at its movable contact 19 and NC contact 23, which operation is thus obtained
Furthermore, when the knob 3 is pressed down into the DOWN state, the slider 28 slides rightward. The push button 27B, abutting against the thick-walled part of slider 28 with respect to its Yxe2x80x94Y section, moves down. The switch B is placed into an open state at its movable contact 20 and NC contact 24, while the same switch B is placed in a close state at its movable contact 20 and NO contact 22, which operation is thus obtained. Meanwhile, when the knob 3 is released from the finger into a neutral state, the slider 28 slides leftward and returns to the former position. The push button 27B moves up, to place the switch B into a close state at its movable contact 20 and NC contact 24, which operation in then obtained.
In the circuit diagram of FIG. 8B, when the knob 3 is in the neutral state, the respective contacts of the switches A and B are in the state shown in the figure, Namely, the switch A is in a close state at between the movable contact 19 and the NC contact 23 while the switch B is in a close state at between the movable contact 20 and the NC contact 24. In this state, because the direct-current motor 2 and the +B line 17 are out of connection and further the potential on ground line 11 (negative power) is applied to both two drive inputs of the direct-current motor 2, the direct-current motor 2 is in a standstill state of rotation. This standstill state of rotation corresponds to the xe2x80x9cmotor stop statusxe2x80x9d described in the gist of the invention.
Meanwhile, in the circuit diagram of FIG. 10B, when the knob 3 is in the UP state, the contacts of the switches A, B are in the state shown in the figure. Namely, the switch A is in a close state at between the movable contact 19 and NO contact 21 while the switch B is in a close state at the movable contact 20 and NC contact 24. In this state, because formed is a close circuit of +B line 17, NO contact 21xe2x86x92direct-current motor 2xe2x86x92NC contact 24xe2x86x92ground line 18, the direct-current motor 2 rotates in a direction closing the window. Provided that the rotation direction is forward, this state of rotation corresponds to xe2x80x9cmotor forward rotation statusxe2x80x9d described in the gist of the invention.
Meanwhile, although not shown, when the knob 3 is in the DOWN state, the switch A is in a close state at between the movable contact 19 and NC contact 23 while the switch B is in a close state at between the movable contact 20 and NO contact 22. In this state, because formed is a reverse rotation close circuit of +B line 17, NO contact 22xe2x86x92direct-current motor 2 NC contact 23xe2x86x92ground line 18, the direct-current motor 2 rotates in a direction opening the window. Provided that the rotation direction is reverse, this state of rotation corresponds to xe2x80x9cmotor reverse rotation statusxe2x80x9d described in the gist of the invention.
Accordingly, the switches A and B of the switch unit 9 in unison are to take a xe2x80x9cmotor stop statusxe2x80x9d to apply negative power (potential on the ground line 18) to both of one drive input and the other drive input of the direct-current motor 2 thereby placing the direct-current motor 2 in a stop state, a xe2x80x9cmotor forward rotation statusxe2x80x9d to apply positive power (potential on the +B line 17) to one drive input of the direct-current motor 2 and negative power (potential on the ground line 18) to the other drive input thereby placing the direct-current motor 2 in a forward rotation state, and a xe2x80x9cmotor reverse rotation statusxe2x80x9d to apply negative power (potential on the ground line 18) to one drive input of the direct-current motor 2 and positive power (potential on the +B line 17) to the other drive input thereby placing the direct-current motor 2 in a reverse rotation state, thus corresponding to xe2x80x9cfist switch meansxe2x80x9d described in the gist of the invention.
Incidentally, although the above explanation showed the example that the one switch unit 9 controls the rotation of the direct-current motor 2, this is not limited to, i.e. on a certain vehicle, there is a switch for making, at the driver""s seat, an open and close operation of the window of another seat (assistant driver""s seat or rear seat).
FIG. 11 is a circuit diagram of the same (see Non-patent Document 1, for example). This circuit is configured by a combination of a driver""s seat switch unit 9 and another seat switch unit 9xe2x80x2. A direct-current motor 2 (direct-current motor for opening/closing an other-seat window) can be rotated and stopped from the driver""s seat besides, of course, from another seat.
Meanwhile, although the above explanation assigned one terminals (common terminals 11, 12 and normally-close terminals 14, 15) respectively to movable contacts 19, 20 and NC contacts 23, 24 while assigning one terminals (normally-open terminals 13) respectively to NO contacts 21, 22 (namely, totally five terminals are provided), this is not limited to. For example, as shown in FIG. 12, it may be a type that the contacts (NC contacts 23, 24 of switches A, B) connected to the ground line 18 are connected together within the unit, and extended from one terminal 15a and connected to the ground line 18 (totally four terminals are provided). Besides, the switch mechanism may be configured by the provision of one circuit, which is arranged two in usage. In this case, totally six terminals are included.
[Non-patent Document 1]
xe2x80x9cToyota*VITZ*Wiring Diagrams/SCP10 System (1999-1 to)xe2x80x9d Toyota Automobile Co., Ltd. Service Department, issued Jan. 13, 1999. p. 3-38 to 3-39.
The switch device (FIGS. 8A, 8B, 9A-9D, 10A, 10B, and 11, and 12) in the prior art explained above operates freely from trouble as long as it is applied to the ordinary 14V-based electrical system. However, where it is applied to an electric system based on the higher voltage, e.g. 42V-based electrical system, a great current possibly flow through the contact connected to the negative power source during returning from the UP state to the neutral state or returning from the DOWN state to the neutral state. There is a problem that this current might cause damage to the relevant contact.
FIGS. 13A to 13C are explanatory diagrams on contact damage, wherein FIG. 13A is a diagram for example in the UP state, FIG. 13B is a diagram of xe2x80x9cimmediately beforexe2x80x9d returning to the neutral state, and FIG. 13C is a diagram of returned to the neutral state. The difference from the explanation of the prior art lies in that a high voltage (power voltage to 42V-based electrical system, hereinafter as xe2x80x9c42Vxe2x80x9d) is applied to the +B line 17.
In the meanwhile, an shown in FIG. 13A, when in the UP state, the switch A 18 in a close state at its NO contact 21 and movable contact 19 while the switch B is in a close state at its movable contact 20 and NC contact 24. Consequently, formed is a close circuit of +B line 17xe2x86x92direct-current motor 2xe2x86x92ground line 18. Thus, the direct-current motor 2 rotate in a direction closing the window.
Then, when the finger is released from the knob 3, the switch A is canceled of the close state at the NO contact 21 and movable contact 19, as shown in FIG. 13B. The movable contact 19 begins to move toward the NC contact 23 while causing an arc discharge 30 having a small allowable range to the NO contact 21.
Finally, as shown in FIG. 13C, the switch A goes into a close state at between the movable contact 19 and the NC contact 23, to cut off the power voltage to the direct-current motor 2. Thus, the direct-current motor 2 is placed in a stop state.
In the case the conventional switch unit 9 is used, the contact gap is as small as approximately 0.5 mm not to secure an arc discharge voltage of 42V, resulting in a connection to the NC contact 23 of the movable contact 19 in a state a several-volt voltage is applied. The experiment conducted by the present inventors has found a trouble that, because at this time a great current 31 (greater than 100A) is to flow in a brief time (approximately 0.5 ms) from the movable contact 19 to the ground line 18 through the NC contact 23, there occurs great discharge phenomenon (hereinafter referred to as xe2x80x9cdead-short) 32 at between the NO contact 21 and the NC contact 23, thereby causing a damage (contact damage or breakdown) to the movable contact 19 and NC contact 23 of the switch A. Such Dead-short 32 is likely to take place particularly in the domain of a contact opening/closing rate (greater than 1000 mm/s) much faster than the ordinary contact opening/closing rate (100 to 400 mm/s).
Because the existence of such trouble prevents against the widespread of 42V-based electrical systems, there is a technical problem to be swiftly resolved in that respect.
Incidentally, as the general countermeasure against arc discharge, it is a practice to broaden the contact gap correspondingly to a magnitude of power voltage. This is because broadening the contact gap (e.g. approximately 4 mm) enables to increase arc discharge voltage so that the movable contact 19 in a state free of voltage application can be connected to the NC contact 23 to thereby avoiding against contact damage. However, this countermeasure, on one hand, involves a problem to incur a great size increase of the switch unit thus preventing against on-vehicle mounting.
Therefore, it is an object of the present invention to provide a switch device capable of avoiding contact damage without incurring a great size increase of a switch unit even where applied to a high power voltage such as a 42V-based electrical system.
The switch device according to the present invention is in a switch device having first switch means capable of taking a motor stop status for applying a negative power to each of one drive input and the other drive input of a direct-current motor thereby placing the direct-current motor in a stop state, a motor forward rotation status for applying a positive power to one drive input of the direct-current motor and a negative power to the other drive input thereof thereby placing the direct-current motor in a forward rotation state, and a motor reverse rotation status for applying a negative power to one drive input of the direct-current motor and a positive power to the other drive input thereof thereby placing the direct-current motor in a reverse rotation state, the switch device comprising:
second switch means for electrically connecting and disconnecting any of between the first switch means and one of the positive power and negative power and between the first switch means and one of one drive input and the other drive input of the direct current motor; and
switch operating means for operating, upon transition of the first switch means from one of the motor forward rotation status and the motor reverse rotation status to the motor stop status, the second switch means from a connection state to a disconnection state at a time of any of completing the transition to the motor stop status and prior to a predetermined marginal period of time.
In this invention, the second switch means is operated from a connection state to a disconnection state at a time of any of completing the transition to the motor stop status and prior to a predetermined marginal period of time. Accordingly, during disconnection in the second switch means, electrical connection is cut off at any of between the first switch means and one of the positive power source and the negative power source and between the first switch means and one of one drive input of the direct-current motor and the other drive input thereof. Accordingly, the first switch means is reduced of the remaining voltage at the contact thereof, thereby eliminating the dead-short problem from the first switch means.
Meanwhile, a preferred embodiment of the invention is characterized in that the predetermined marginal period of time is taken approximately 1 ms.
In this embodiment, due to so-called a double-breakeffect, the power voltage (potential difference between the positive power source and the negative power source) can be shared, approximately half and half (approximately 21V on each in the case of a 42V-based electric system), by the first and second switch means. Accordingly, even in case the switch device under the specification of 14V-based electric system is used in the first switch means or second switch means, there is no possibility to cause dead-short.